added the sign-up button on the upper right
added new servlet for sign up
added subjectCode attribute for ClassBean
included the subjectCode in FetchClassList
refactored design of html tags and code
changed one data in sql
refactored parameter from ArrayList<Student> to ArrayList<String>
since only the name is needed.
FetchStudentList was also modified
changed data in database
added a subjectList attribute
git demo